Field of the Invention
The present invention relates to a developer container for housing a developer used to form an image on a recording medium. The present invention further relates to a process cartridge which forms a developer image on a photosensitive drum and which is attachable to and detachable from an image forming apparatus, and to an image forming apparatus which forms an image on a recording medium using a developer.
Description of the Related Art
With an image forming apparatus such as a printer which uses an electrophotographic image formation system (an electrophotographic process), when an image is formed on a recording material, a photosensitive drum is first uniformly charged by a charging roller. Next, the charged photosensitive drum is selectively exposed by an exposing apparatus to form an electrostatic latent image on the photosensitive drum. In addition, the electrostatic latent image formed on the photosensitive drum is developed as a toner image using toner by a developing apparatus. Subsequently, the toner image formed on the photosensitive drum is transferred onto a recording material such as recording paper or a plastic sheet, and the toner image transferred onto the recording material is fixed to the recording material by being subjected to heat and pressure by a fixing apparatus. In this manner, an image is formed on the recording material. In addition, toner that remains on the photosensitive drum after the toner image is transferred to the recording material is removed by a cleaning blade.
With such an image forming apparatus, generally, processing means such as a photosensitive drum, a charging roller, and a developing apparatus require maintenance. In recent years, in order to facilitate the maintenance of such processing means, the photosensitive drum, the charging roller, the developing apparatus, and a cleaning blade are integrated into a cartridge. Generally, a cartridge including such processing means is called a process cartridge. The process cartridge can be attached to and detached from an apparatus main body of the image forming apparatus and, by replacing the process cartridge, processing means can be replaced and maintenance can be performed thereon.
Conventionally, in-line system image forming apparatuses are known in which a plurality of photosensitive drums are approximately horizontally arranged and in which a toner image on the photosensitive drums is transferred to a recording material via an intermediate transfer belt. In addition, in such image forming apparatuses, there are those in which the plurality of photosensitive drums, a developing apparatus, and an exposing apparatus are arranged below the intermediate transfer belt. When the photosensitive drums, the developing apparatus, and the exposing apparatus are arranged below the intermediate transfer belt, the photosensitive drums, the developing apparatus, and the exposing apparatus are to be arranged inside the image forming apparatus on an opposite side of a fixing apparatus with respect to the intermediate transfer belt. Therefore, the photosensitive drums, the developing apparatus, and the exposing apparatus can be arranged at distant positions from the fixing apparatus. Accordingly, an impact of heat from the fixing apparatus on the photosensitive drums, the developing apparatus, and the exposing apparatus can be suppressed.
As described above, when the photosensitive drums, the developing apparatus, and the exposing apparatus are arranged below the intermediate transfer belt, generally, a developing chamber in which is arranged a developing roller bearing toner to be used in development is arranged above a toner storage chamber in which toner is stored. In addition, the developing chamber and the toner storage chamber communicate with each other via an opening. In such a developing apparatus, the toner stored in the toner storage chamber must be conveyed through the opening and to the developing chamber arranged above the toner storage chamber against gravity.
In consideration thereof, conventionally, a sheet-like stirring member is provided in the developing apparatus (the developer container) and, by rotating, the stirring member kicks up toner accumulated at a bottom of the toner storage chamber into the developing chamber. Specifically, the sheet-like stirring member rotates around an axis of a rotational center extending approximately in a horizontal direction to lift up toner accumulated at the bottom of the toner storage chamber. In addition, in a state where the stirring member is lifting up the toner, the stirring member comes into contact with an inner wall surface of the toner storage chamber and deflects. Subsequently, as a contact state between the inner wall surface of the toner storage chamber and the stirring member is released, the stirring member is restored to its original shape and toner on the stirring member is kicked up into the developing chamber against gravity by the restorative force.
A developer container is generally provided with a developing roller which is rotatably supported against a frame of the developer container and a developing blade which adjusts a layer thickness of toner borne by the developing roller. In addition, the developer container is provided with a sheet member which closes a gap between the frame and the developing roller of the developer container so as to prevent toner from leaking out from the gap between the frame and the developing roller. Furthermore, the developer container is provided, in a vicinity of ends in an axial direction of a rotational center of the developing roller, with a seal member for closing a gap between the developing roller and the frame, a gap between the developing blade and the frame, and a gap between the sheet member and the frame. Accordingly, leakage of the toner inside the developer container to an exterior of the developer container is suppressed. However, when pressure inside the developer container rises, a pressure difference is created between an interior and the exterior of the developer container, thereby creating a risk that toner may leak out from a gap between the sheet member and the developing roller or gaps between the frame of the developer container and the like and the seal member.
With a technique disclosed in Japanese Patent No. 5751779, in a configuration in which a developing chamber is arranged below a toner storage chamber, an opening is provided on an inner wall of the developing chamber and the opening is covered by an air-permeable filter. Accordingly, even when an impact is applied to the developing apparatus, since air is discharged from the opening and pressure inside the developing chamber decreases, toner can be prevented from leaking out of the developing apparatus.
In addition, with a technique disclosed in Japanese Patent No. 4790676, a developing chamber is not provided in a developing apparatus and a developing roller is arranged above a screw for conveying toner inside a toner storage chamber. Furthermore, an opening is provided on an inner wall of the toner storage chamber and the opening is covered by an air-permeable filter. When an air flow is created toward the opening, an air flow created by a rotation of the developing roller causes toner floating inside the developing apparatus to be captured by the filter.
With a developer container in which a sheet-like stirring member supplies toner into a developing chamber, a rotation of the stirring member causes the stirring member to convey not only the toner but also air into the developing chamber. Therefore, when pressure inside the developer container rises as the stirring member rotates and a pressure difference is created between the interior and the exterior of the developer container, a risk is created in that toner may leak out from a gap between the sheet member and the developing roller, a gap between the frame of the developer container and the seal member, and the like.
Furthermore, recent increases in image formation speed (printing speed) of image forming apparatuses call for a larger amount of toner to be supplied to a developing chamber. In order to do so, a rotational speed of a sheet-like stirring member must be increased or a thickness of the stirring member must be increased.
However, in such cases, since a larger amount of air is conveyed inside the developing chamber by a rotation of the stirring member, pressure inside the developing chamber rises and, consequently, a risk is created in that toner may leak out from a gap between a sheet member and a developing roller and the like as described above.